11cc outboard shims

[HOOTERS Racing]

hi all

im getting ready to start a new 11cc k&b o/b it will be running on 30% fuel

and rich but i was just wondering if i should take the 2 head shims out

all my other motors (7.5cc) have had the shims taken out any imput

would be tops thanks

ian

 

[Jerry Wyss]

Hey Ian, It would be very risky to just take the shims out without knowing what clearance you have now.

With a K&B, they're tolerance in this area "has been" all over the place, say .8 to .5mm. If I didn't have

any other source of measuring equipment I guess I would cut off a small chunk of candle wax, place it

on the piston top , re-assemble and smash it. Compare the smashed wax to a simple "feeler guage" and

see what you have. I would run no less than .457mm (.018") with that fuel for a while and I would also

pinch the water down some to get the P&L to swell enough for a good break-in. I have ruined many a P&L

by running them too cold in the past, it just wears the life right outa them.

This is not an "opinion", it's what I would do if I had no other means of measuring.

JW

 

[HOOTERS Racing]

Hey Ian, It would be very risky to just take the shims out without knowing what clearance you have now.With a K&B, they're tolerance in this area "has been" all over the place, say .8 to .5mm. If I didn't have

any other source of measuring equipment I guess I would cut off a small chunk of candle wax, place it

on the piston top , re-assemble and smash it. Compare the smashed wax to a simple "feeler guage" and

see what you have. I would run no less than .457mm (.018") with that fuel for a while and I would also

pinch the water down some to get the P&L to swell enough for a good break-in. I have ruined many a P&L

by running them too cold in the past, it just wears the life right outa them.

This is not an "opinion", it's what I would do if I had no other means of measuring.

JW

hey mate thanks for that i will do that then how high could i go with the nitro % im useing 50% in my 3.5 and 7.5

thanks ian

 

[Jerry Wyss]

hey mate thanks for that i will do that then how high could i go with the nitro % im useing 50% in my 3.5 and 7.5 thanks ian

It's been a long time since I ran the K&B's , I also was running 50% in that .016 to .018" headspace area with more

exhaust port and crank closing timing over stock. I think I was only 3 degrees over the 2 stock timings listed and I ran

a longer stinger on the Aerotech pipe which gave me more fuel pressure and heated the motor up more. The plug

elements would be slightly drawn outa they're sockets after a hot run but it was worth it after seeing it go so well.

I was running the lighter DPI plastic 48" tunnel modified so it would actually turn the way I needed it to turn for the

oval course. They were a fun boat once modded, I even added a spar up front and inside the hull to tie the sponsons

to the center section of the hull. Blow off's , rough water poundings and increased cornering forces would ultimately

do'em in. I went thru three of them boats in a couple seasons,, best prop was a X452 (I think) that I dicked with for

a while to get the motor to wind up,, I had a couple good running 11's.

The Geraghty carbs were a huge improvement over the stock unit,, the stock carbs worked perdy well but they would

just "eat" themselves quickly due to the vibration of the rotating barrel. They were the carb that was between the carb

with the removable velocity stack and the one with the brass disc for the low speed.

That's all I remember

JW